The biggest issue with energy usage in the data centre is not how it is used within the data centre itself, but the way that it’s generated and distributed and the losses incurred before it even reaches the point of use.

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The fact that many different voltages are used in the transmission and distribution of energy means that energy is transformed several times, and each transformation produces efficiency losses. Choosing the right form of power generation and where it is situated provides greater energy sustainability and can lower the carbon impact of a data centre.

If a data centre is powered directly from a national power grid infrastructure, very little can be done about these losses, but at least you can choose a generator with less carbon impact (eg, hydro, nuclear and geothermal) in many cases. Even though the electrons used by the equipment may have come from fossil fuel generation, such contracts encourage further investment in non-fossil fuel systems and continue the move towards more sustainable systems. Transmission and distribution losses will be the same, but eliminating fossil fuels from the equation at least lessens the carbon impact.

High/low voltage and data centre power generation

Transmission losses are based on the resistance of the cables carrying the power, so the shorter the transmission link, the better. High-voltage AC transmission is more efficient than lower-power AC or DC distribution, as the power losses are more dependent on current than on voltage. Therefore, ensuring that the data centre has its own substation with optimised low-voltage distribution minimises losses because the data centre owner has control over the supply.

More data centre owners, however, are looking at changing their approach to the initial power generation needed by moving the data centre closer to the generator or integrating generation as part of the data centre itself. For example, Yahoo opened a data centre in Quincy, Wash., US, that uses locally produced hydroelectric power that has fewer losses in the short distance between the point of generation and usage. In addition, it uses natural air cooling, which eliminates the need for electricity for cooling – an area which is often more energy-intensive than the IT equipment itself.

Hydro power, geothermal power, solar and wind power management

Quincy has become a focal point for high-tech data centres, with Microsoft also having an air-cooled, hydropowered data centre there, and Dell and Sabey both building large facilities that can make use of the large amounts of hydropower in the area.

In a similar move, Iceland has been marketing itself as a place to build data centres with access to unlimited cheap energy, but there it’s based on geothermal power. A prime example in Iceland is the Thor data centre; it’s more energy efficient because of lower transmission and distribution losses, and it also has zero incremental carbon impact from the generation itself. Additionally, the year-long low external temperatures make it feasible to air-cool a data centre.

Fujitsu, Verizon and First Bank of Omaha are all running data centres that use hydrogen-powered fuel cells as part of their main energy feed. It’s touted as a low-impact energy source as the output from a hydrogen fuel cell is just electricity, heat and water. But, the amount of energy required to create the hydrogen in the first place can make such an approach ineffective overall if the energy for cracking hydrogen from water or petrochemicals comes from fossil fuels originally.

Although not yet used for powering data centres on their own, solar and wind power can at least be used for powering some of the more peripheral aspects of the data centre. For example, Co-operative Insurance (CIS) in the UK has covered one side of its headquarters in Manchester with photovoltaic and has the capacity to generate 180,000 units of energy per year. It’s nowhere near enough for a data centre itself, but it’s plenty for lighting and ancillary needs.

Other World Computing (OWC) uses wind power to power its data centre in Woodstock, Ill., US, but it has to depend on the grid for power when there is insufficient wind. However, the reduction of both CIS and OWC’s carbon footprint is significant enough to make the approaches worthwhile.

Within the data centre itself, the question of only using AC for distribution to equipment or using DC throughout the data centre is still an item for discussion. A couple of years ago, DC seemed to be a far better choice, but the need for equipment in the data centre to be built specifically for DC use, and for data centre wiring and distribution architectures to be specific to DC, seems to have pushed data centre owners to stick with AC.

Furthermore, for DC to provide the promised energy efficiencies, it’s preferable for all equipment to use the same voltage – and this is highly unlikely. There will still be the need for multiple transformations to the main 12 V, 5 V and 3.3 V outputs used at the equipment level.

The benefits of structured cabling

Structured cabling can ensure that losses are minimised in many cases and that the right cabling is used for specific jobs. Plus, low-power systems can be powered over Ethernet connections rather than having dedicated power links. In addition, ensuring cables are not looped or otherwise positioned to create power drains through interaction with each other can save small amounts per feed, which in a modern data centre can soon mount up to considerable overall energy savings.

Making sure that a data centre is both energy efficient and energy effective requires careful thought and implementation. The means of power generation, the most effective means of transmission -- preferably over the shortest distances possible with the most modern transformers -- and fully structured power management cabling will enable energy to be saved and sourced with a lower carbon impact than standard fossil sources. If done with the right forethought, it will also provide flexibility and enable new equipment and architectures to be embraced as needed.

Clive Longbottomis a service director at UK analyst Quocirca Ltd. and a contributor to SearchVirtualDataCentre.co.UK.

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